570 



THE ILLINOIS GLACIAL LOBE. 



the county is traversed from north to south by Rock River, the northwestern 

 portion is traversed from west to east by the Pecatonica, and the southeast- 

 ern portion from east to west by the Kishwaukee River. 



The portion of the county west of Rock River has generally a thin 

 coating of drift, except in the preglacial valleys. The majority of wells on 

 the uplands enter rock at less than 20 feet. There are, however, occasional 

 wells located probably over tributaries of the preglacial Rock or Pecatonica 

 which penetrate 75 feet or more of drift without reaching the rock. Excel- 

 lent exposures of the drift may be seen along the line of the Illinois Central 

 Railway between Rockford and Freeport. Like the drift of Stephenson 

 County, it is generally very stony and contains a considerable amount of 

 gravel and sand. Much of this portion of the county is covered with a 

 loess-like silt 4 or 5 feet in thickness, which furnishes an excellent soil. 



The portion of the county east from Rock River carries a heavy 

 deposit of drift, rock seldom being found at less than 100 feet, and it is 

 probable that along the valley of Rock River and its immediate borders the 

 thickness exceeds 300 feet, for borings to the north and south show that the 

 rock floor of the preglacial valley stands 250 to 300 feet below the present 

 stream bed. The drift of the eastern portion of the county embraces a 

 sheet which extends but little west of Rock River and which, as indicated 

 above, is referred to the Iowan stage of glaciation. 



INDIVIDUAL WELLS. 



A large number of well sections were collected by Mr. I. M. Buell 

 during his investigation of the drumlins and bowlder distribution of Winne- 

 bago and Boone counties. But few records have been obtained by the 

 writer. Mr. Buell has kindly turned over these well records for presenta- 

 tion in this report, and they appear in the table below. The}^ are chiefly 

 found in the district east of Rock River. 



Table of well sections east of Rock River in Winnebago County, Illinois. 



